Hello ApostlepaulAkpan,
I'm Jin, a fellow Windows 10 user and an independent advisor. I understand that the SHIFT+3 generates a £ sign instead of #.
To start troubleshooting, follow the steps provided on this link:
https://windowsreport.com/hash-key-not-working/
This is a non-Microsoft website which would provide accurate and safe information. Watch out for ads on the site which are frequently classified as a PUP (Potentially Unwanted Products). There is no need to buy paid products to fix your computers as they do more harm than good sometimes.
In the meantime, you can also use the shortcut ALT+35 to generate # sign.
Hope this helps.